Polystyrene peroxidation resistance

Initiators (1) and (2) have 10-h half-life tempeiatuies of 237°C and 201°C, respectively. It has been reported that, unlike organic peroxides and ahphatic azo compounds, carbon—carbon initiators (1) and (2) undergo endothermic decompositions (62). These carbon—carbon initiators are useful commercially as fire-retardant synergists in fire-resistant expandable polystyrenes (63). 

One of the primary fields of application for P.R.151 is in polystyrene, although there is a slight color change at temperatures above 260°C, at which the pigment partially dissolves. It is also used to a considerable extent in ABS. Cast resins based on methylmethacrylate and unsaturated polyesters are also frequently colored with P.R.151, which is resistant to the peroxide catalysts that are used to harden the plastic. The lightfastness in these media is good it equals step 6-7 on the Blue Scale. 

Commercial poly(butadiene), which is mainly the 1,4 isomer, is also used to improve the impact resistance of polystyrene (Chapter 1). Polydienes also increase the rate of physical disintegration of polyblend containing them. The addition of a styrene-butadiene block copolymer e.g. SBS, page 9 et seq.) to polyethylene also accelerates the peroxidation of the latter. However, this system also requires a polymer-soluble transition metal ion catalyst e.g. an iron or manganese carboxylate) to increase the rate of photooxidation in the environment by the reactions shown in Scheme 5.3. The products formed by breakdown of alkoxyl radicals (PO ) (Scheme 3.4) are then rapidly biodegradable in compost (page 107 et seq.). 

Polystyrene is very difficult to cross-link by electron beam radiation or by peroxide without destroying its properties. As a result, applications have not been developed. The methyl groups of poly-PMS, by contrast, provide susceptible positions for such a reaction. PMS polymers can be cross-linked effectively by electron-beam radiation. This unique property of tpoly-PMS could open several new markets. Crosslinking turns a PMS-based thermoplastic into a thermoset resin, significantly improving its grease resistance and flammability behavior. 

The condensation reaction between MA and aliphatic or aromatic polyamines has been used to prepare a large number of bismaleimides - - - and trismaleimides. """- "" Polystyrene has been treated with A-chloromethyl-maleimide, using a mild Friedel-Crafts procedure, to prepare polymer with pendant maleimide residues.Poly(vinyl alcohols) and alternating styrene-MA copolymer or polymers with pendent epoxide residues " have been converted to polymers with pendent maleimide moieties. All these multifunctional maleimides may be polymerized thermally, with peroxides, UV light, and y rays to obtain heat-resistant coatings or lami-... 

Polystyrene is relatively resistant to oxygen at room temperature. With increasing temperature, oxidative atmosphere leads to degradation phenomena and discoloration. The reaction of formed primary radicals into a peroxide radical represents the start of oxidative degradation. Figure 5.175. 

Organic peroxides can occur in small amounts in some types of polymers such as polystyrenes as a result of the fact that a peroxide has been used as a polymerization catalyst in polymer manufacture. Also, stable organic peroxides such as dicumyl peroxide has been used as synergists, in conjunction with bromine and or phosphorus containing additives, to impart Are resistance to cellular expanded polystyrene and other types of plastics... 

TPEs of SBS (and SEBS)-type are versatile. Compared to PVC compounds, ester plasticizers cannot be used in TPE compounds. Vulcanizing agents such as accelerators, sulfur, or peroxides are not required in SBS-type TPE block copolymers. EPDM is blended with SBS to increase ozone resistance. PS, polyethylene (LDPE, LLDPE, HDPE), and polypropylene (PP) are used as additive polymers with SBS and SEBS. Polystyrene (PS) is compatible with B-S block copolymers. Polystyrene is useful to adjust properties and cost of SBS compounds. The addition of polystyrene into SBS increases hardness, modulus, tensile strength, tear strength, and abrasion resistance. Styrenic resin (a-methyl styrene) can be used as a blend with PS or as an alternative for SBS compound. This resin can be used as a blend with polystyrene as an alternative. Styrenic resin enhances flow properties and physical properties. It is more compatible compared to polystyrene and assists in adhesion and coherent processing. 

Precipitation in methanol has shown that many commercially available styrenated alkyds are blends of the alkyd and polystyrene. An attempt to produce copolymers by adding styrene and benzoyl peroxide or di-tert-bulyl peroxide to a commercial soy-linseed medium alkyd (Cargill Company Alkyd Resin Product No. 5150) in a nitrogen atmosphere, were also unsuccessful. However, blends containing at least 40% styrene were compatible with the alkyd resin, and the coatings were slightly hazy, last drying, harder, and more chemical resistant than the alkyd resins component. 

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